Problem: My non optional variable is nil. (Fatal Error while unwrapping)

Question

I am trying to update an UILabel.

@IBOutlet weak var balanceLabel: UILabel!

it is initially declared as a non optional variable:

var balanceValue: Int = 1

The UILabel depends on the not optional variable balanceValue.

func updateBalanceLabel() {
        balanceLabel.text = String(balanceValue) }

That all worked fine, but at some point I got this fatal error, which wont go away:

Thread 1: Fatal error: Unexpectedly found nil while implicitly unwrapping an Optional value

The error is referring to this line:

balanceLabel.text = String(balanceValue)

That does not make any sense... I am having a non optional variable which is declared as 1 per default. How can it be nil.

Here is the crashlog:

> libswiftCore.dylib`_swift_runtime_on_report:
->  0x7fff51b801c0 <+0>: pushq  %rbp 
    0x7fff51b801c1 <+1>: movq   %rsp, %rbp
    0x7fff51b801c4 <+4>: popq   %rbp
    0x7fff51b801c5 <+5>: retq   
    0x7fff51b801c6 <+6>: nopw   %cs:(%rax,%rax)

and

ibswiftCore.dylib`Swift._assertionFailure(_: Swift.StaticString, _: Swift.String, file: Swift.StaticString, line: Swift.UInt, flags: Swift.UInt32) -> Swift.Never:
    0x7fff518d9370 <+0>:  pushq  %rbp
    0x7fff518d9371 <+1>:  movq   %rsp, %rbp
    0x7fff518d9374 <+4>:  movl   0x28(%rbp), %eax
    0x7fff518d9377 <+7>:  movl   0x18(%rbp), %r10d
    0x7fff518d937b <+11>: pushq  %rax
    0x7fff518d937c <+12>: pushq  0x20(%rbp)
    0x7fff518d937f <+15>: pushq  %r10
    0x7fff518d9381 <+17>: pushq  0x10(%rbp)
    0x7fff518d9384 <+20>: callq  0x7fff51adf410            ; function signature specialization <Arg[0] = Exploded, Arg[1] = Exploded> of Swift._assertionFailure(_: Swift.StaticString, _: Swift.String, file: Swift.StaticString, line: Swift.UInt, flags: Swift.UInt32) -> Swift.Never
->  0x7fff518d9389 <+25>: addq   $0x20, %rsp
    0x7fff518d938d <+29>: ud2    
    0x7fff518d938f <+31>: nop

What weirds me out, that I did not change the working code, but now all of a sudden I get this problem. Restarting XCode wont solve it. Tried different things to pin down the problem, but I cant find the reason why balanceValue should be nil. Any help greatly appreciated.

Can you add a breakpoint and check what is the value of `balanceValue` in the function `updateBalanceLabel`? — Rob, Jan 28 '20 at 06:24
try to check `balanceLabel` @IBOutlet connected to storyboard — Kishan Bhatiya, Jan 28 '20 at 06:27
@Rob I dont know how to use breakpoints. But I added a print right before the line of the error: 'func updateBalanceLabel() { print(balanceValue) balanceLabel.text = String(balanceValue) }' And it prints 111 — Roman P., Jan 28 '20 at 06:33
This is the console: 111 'Fatal error: Unexpectedly found nil while implicitly unwrapping an Optional value: file /Users/roman/Desktop/vToken/vToken/ViewController.swift, line 87 2020-01-28 13:30:18.234060+0700 vToken[5719:617245] Fatal error: Unexpectedly found nil while implicitly unwrapping an Optional value: file /Users/roman/Desktop/vToken/vToken/ViewController.swift, line 87 (lldb) ' — Roman P., Jan 28 '20 at 06:34
Check your `storyboard` you must not have connected the `IBOutlet`. — Rob, Jan 28 '20 at 06:34
@KishanBhatiya Yes it is connected https://imgur.com/a/m0hSPpf — Roman P., Jan 28 '20 at 06:37
@Rob I just rechecked, disconnected, and connected it again. Still same error... — Roman P., Jan 28 '20 at 06:39
@RomanP. Can you try this: `balanceLabel.text = "\(balanceValue)"`? — Rob, Jan 28 '20 at 06:43
@Rob balanceLabel.text = "\(balanceValue)" still throws the same fatal error... — Roman P., Jan 28 '20 at 06:49
@RomanP. Thanks for the update. I guess now it worked for you. — Rob, Jan 28 '20 at 06:50
@RomanP. now you got solution but once try to check create another label and assign value to it — Kishan Bhatiya, Jan 28 '20 at 07:07

Afsar edrisy · Answer 1 · 2020-01-28T06:41:22.597

1

Check balanceLabel if nil or not, balanceValue is not optional so the error which you are getting is due to balanceLabel only. Use blow method


func updateBalanceLabel() {

     guard let label = self.balanceLabel else{
       print("balanceLabel found nill ")
       return 
   }
    label.text = String(balanceValue)


}

After executing this if you are getting balanceLabel found nill then you should check outlet & connect it to UILabel in storyboard.

edited Jan 28 '20 at 06:41

answered Jan 28 '20 at 06:35

Afsar edrisy

1,985
12
28

You are right. it prints: tierLabel found nill Reconnecting outlets did not help. – Roman P. Jan 28 '20 at 06:46
then connect your outlet to UILabel by clicking on circle in front of balanceLabel + ctrl and drag to UILabel in storyboard – Afsar edrisy Jan 28 '20 at 06:48

score 0 · Accepted Answer · answered Jan 28 '20 at 06:32

0

Its nil because your outlet is broken. Since you declared it as an implicitly unwrapped optional, balanceLabel.text = String(balanceValue) is the same as balanceLabel!.text = String(balanceValue). You can verify this is tru by simply using optional unwrapping (an implicitly unwrapped optional is still an optional): balanceLabel?.text = String(balanceValue). Go into your storyboard, right click the label and look at the connections. break any existing connections and then recreate the binding to your variable.

answered Jan 28 '20 at 06:32

Josh Homann

15,933
3
30
33

Thanks. Exactly as you said. Once I added the ? to balannceLabel?.text, the error jumped to the next function. In the end I had to add ? to all functions. Breaking and recreating bindings to variable did nothing for me tho. Now the question remains why it happened all of a sudden. First it worked fine the way I wrote it. – Roman P. Jan 28 '20 at 06:45

Problem: My non optional variable is nil. (Fatal Error while unwrapping)

2 Answers2